Question

Give a detailed account of eye structure and its function?

Answer 1

The eyes are set within the eye sockets of the skull. They are protected in various ways, the most obvious being the eyebrows and the eyelids. Adipose tissue in the eye sockets serves as a cushioning. The lachrymal glands, or tear glands, secrete a fluid which helps to flush out foreign particles and prevent infection. The eyeball is nearly spherical and has three layers. The outermost of these is the sclera followed by the choroid and the retina. 1) - Sclera is opaque, except for its front portion, which is transparent and thus allows light to enter. Transparent area is known as cornea. The sclera Is made of fibrous connective tissue, and is thick and tough and maintains the shape of eyeball. The cornea is covered by the Conjuctiva, a protective membrane which is thin and transparent. It extends to line the surface of the eyelids as well. 2) - Choroid is a pigmented layer with a network of capillaries which supply blood to the eye . Choroid runs along the inner surface of the sclera, but bends inwards where the cornea starts and forms iris which determines the colour of the eye. Iris also regulates the amount of light entering the eye. At its centre there is a hole, pupil which allows light to pass to the lens - which converges light to retina to form image. A part of choroid near the lens forms ciliary processes which alters the shape of the lens. 3) - Retina has two types of light receptors, called rods and cones. Rods are sensitive to dim light, while cones are sensitive to bright light and the various colours. Nerve fibers arising from the rods and cones go on to form the optic nerve at the back of eyeball which carries the impression of the image formed to the brain